<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1.0">
    <title>mydemo</title>
  </head>
  <body>
    <div id="app"></div>
    <!-- built files will be auto injected -->
  </body>
  <script>
  fnResize()
  window.onresize = function () {
    fnResize()
  }

  function fnResize() {
    var deviceWidth = document.documentElement.clientWidth || window.innerWidth
    if (deviceWidth >= 750) {
      deviceWidth = 750
    }
    if (deviceWidth <= 320) {
      deviceWidth = 320
    }
    document.documentElement.style.fontSize = (deviceWidth / 7.5) + 'px'
  }
  </script>
</html>
